LTCJack, haha, Atlanta is very hot this time of year right?
For your Rotel, you have to connect it to the PreOut jacks (they are marked PREOUT with the terminals for FR, FL, C, SR, SL). Connect these to corresponding 5 RCA inputs of your Rotel called RIGHT FRONT, LEFT FRONT, INPUT CENTER, RIGHT, SURROUND, LEFT SURROUND). ANd then connect up the 5 speakers to the Rotel instead of your Denon.
As for the volume of your second zone,
First I assume you have the speakers connected to the SURROUND BACK/AMP ASSIGN terminals
I'm not sure you mean by the volume coming on louder in your other room. On your remote, after you select the Zone Select to Zone 2, you should be able to control the receiver independently of the normal main room settings, so you can control the volume independent for that zone.